The accessory gearbox, well-known to a person skilled in the art under the term AGB, supports different auxiliary equipment or accessories, mounted on the engine and required for its operation or that of the aircraft. These various accessories can in particular comprise a generator, a starter, fuel or oil hydraulic pumps, and are driven mechanically by the engine shaft through intermediate drive shafts. The necessary power for driving the accessories is generally drawn mechanically from the compressor of the turbomachine.
Usually, the AGB comprises parallel-axis gearing to mechanically drive the accessories. The separation of the accessories is therefore determined by the center distance between the gearing, and not by their respective bulk. To increase this separation, one or more intermediate gears are therefore necessary, which has the disadvantage of increasing both the bulk of the AGB and its mass. Moreover, the axes of all the gearing of the AGB being parallel, the accessories have necessarily the same orientation with respect to the AGB and the engine.
Moreover, in the case of a turbofan, the gas generator is connected to a fan which is housed in a fan casing. The nacelle then has a generally circular cross-section. The space available for housing the AGB is consequently defined as an annular portion housed in the nacelle, surrounding the turbomachine, and consequently having generally curved shape (see FIG. 1).
In comparison, in the case of a turboprop, the gas generator causes a propeller to rotate through a propeller gearbox. The propeller is not housed in a casing, and the nacelle has a generally rectangular cross-section. The space available to house the AGB is therefore different from that of turboprops, and extends principally above and below the turbine engine, with a slight space on the lateral flanks.
The conventional AGBs of turbojets are therefore not adapted from a structural, dimensional and functional point of view to turboprops, particularly those with low power comprising a non-coaxial gearbox for a propeller. Moreover, the Applicant realized that conventional AGBs do not allow accessories to be spread over a relatively large angular sector of the periphery of a turboprop nacelle, and in particular do not allow installing accessories both on top of the casing of the turboprop and along at least one of its flanks.
For example, document U.S. Pat. No. 5,687,561 describes an engine of a turbojet comprising a gearbox for the accessories of an engine comprising an engine shaft, intended to mechanically drive at least two accessories, each having a transmission shaft. The configuration and the means for driving the accessories are not specified, however.
Document EP 2 455 597, for its part, describes an engine comprising a gearbox for accessories with parallel-axis gearing, comprising an engine shaft intended to mechanically drive at least two accessories each comprising a transmission shaft.
Finally, document U.S. Pat. No. 1,832,111 describes a gearbox comprising a primary drive shaft and angle gears. This gearbox is however not suited for use in a turboprop.